System and method for performing segment routing over an MPLS network

ABSTRACT

A method for controlling packet routing in a network includes identifying segment identifications (IDs) for a number of switches and arranging a first number of the segment IDs into a multi-protocol label switching (MPLS) label field. The method further includes identifying an output port of a respective one of the number of switches located along a network path between source and destination nodes. The switches may route the packet based on corresponding ones of the segment IDs in the MPLS label field. In performing this routing operation, each switch may modify the MPLS label field with remaining ones of the segment IDs that have been shifted in position and padded with zeros, after the segment ID corresponding to the switch has been popped from the MPLS label field. The method therefore presents a technique for performing segment routing through network equipment designed to support MPLS routing.

TECHNICAL FIELD

This disclosure relates generally to networks, and more specifically,but not exclusively, to controlling the routing of packets in acommunications network.

BACKGROUND

Multi-protocol Label Switching (MPLS) is a technique used to route datathrough a communications network. Unlike other techniques which usenetwork addresses to control routing, MPLS routes data packets acrossnodes using labels. These labels identify virtual links (paths) betweendistant nodes, rather than endpoints, and are useable with differentnetwork protocols (e.g., T1, E1, ATM, Frame Relay, DSL, etc.), hence theterm “multi-protocol” label switching.

Routing data using MPLS is advantageous in a number of respects. Forexample, MPLS is able to perform routing without the use of complexlookups in a routing table. Using labels (as opposed to comprehensivenetwork addresses) also increases the rate of traffic flow. For theseand other reasons, many networks today use equipment designed toimplement MPLS routing. However, this equipment is restrictive in naturein that it prevents the networks from supporting other types of routingtechniques. Segment routing is a new routing technique that isspecifically designed for MPLS networks.

SUMMARY

A brief summary of various example embodiments is presented. Somesimplifications and omissions may be made in the following summary,which is intended to highlight and introduce some aspects of the variousexample embodiments, but not to limit the scope of the invention.Detailed descriptions of example embodiments adequate to allow those ofordinary skill in the art to make and use the inventive concepts willfollow in later sections.

In accordance with one or more embodiments, a method for controllingpacket routing in a network includes identifying segment identifications(IDs) for a number of switches and arranging a first number of thesegment IDs into a first field of a packet, wherein the first field is afirst multi-protocol label switching (MPLS) label field that is M bitsin length, each of the segment IDs being represented by N bits in lengthand identifying an output port of a respective one of the number ofswitches located along a network path between a source node and adestination node, wherein M is greater than a cumulative sum ofrespective Ns for the first number of segment IDs. The first number ofsegment IDs may be arranged in the first MPLS label field in an ordercorresponding to a sequence of the number of switches on the networkpath. The method may include padding the first MPLS label field with oneor more predetermined values for bits unoccupied by the segment IDs. Theone or more predetermined values may be zeros.

The first number of the segment IDs arranged into the first MPLS labelfield may correspond to all of the switches on the network path betweenthe source node and the destination node. Each of the segment IDs may becompressed into N bits. In one embodiment, the value of N may be atleast 3. The method may include arranging a second number of the segmentIDs into a second field of the packet when the number of switches isgreater than three, where the second field of the packet is a secondMPLS label field. The method may include identifying the segment IDsbased on information in a routing table.

In accordance with one or more embodiments, a method for controllingpacket routing includes receiving a packet at a switch of a datanetwork, accessing first routing information from the packet, modifyingthe packet to include second routing information, and transmitting thepacket from the switch based on the first routing information, whereinthe packet includes a first multi-protocol label switching (MPLS) labelfield from which the first routing information is accessed, the firstrouting information including a first segment identification (ID) and atleast a second segment ID, and wherein modifying the packet includesreplacing the first routing information with the second routinginformation in the first MPLS label field, the second routinginformation omitting the first segment ID and including at least thesecond segment ID, the packet transmitted from the switch based on thefirst segment ID.

The method may include replacing the first routing information with thesecond routing information includes replacing the first segment ID withone or more predetermined values in the first MPLS label field. The oneor more predetermined values may be zeros. The method may includereplacing the first routing information with the second routinginformation includes shifting a position of the at least second segmentID in the first MPLS label field. The method may include determining anoutput port number based on the first segment ID, wherein transmittingthe packet based on the first routing information includes transmittingthe packet through the output port number.

In accordance with one or more embodiments, a system for controllingpacket routing in a network comprises a memory configured to store atleast one algorithm and a processor configured to execute the at leastone algorithm to identify segment identifications (IDs) for a number ofswitches, and arrange a first number of the segment IDs into a firstfield of a packet, wherein the first field is a first multi-protocollabel switching (MPS) label field that is 20 bits in length, each of thesegment IDs being N bits in length and identifying an output port of arespective one of the number of switches located along a network pathbetween a source node and a destination node.

The processor may arrange the first number of segment IDs in the firstMPLS label field in an order corresponding to a sequence of the numberof switches on the network path. The processor may pad the first MPLSlabel field with one or more predetermined values for bits unoccupied bythe segment IDs. The first number of the segment IDs arranged into thefirst MPLS label field may correspond to all of the switches on thenetwork path between the source node and the destination node. Theprocessor may arrange a second number of the segment IDs into a secondfield of the packet when the number of switches is greater than three,and wherein the second field of the packet is a second MPLS label field.The first MPLS field may have a length of 20 bits, each of the firstnumber of segment IDs may be compressed into N bits.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures together with the detailed description below,are incorporated in and form part of the specification, and serve tofurther illustrate example embodiments of concepts found in the claimsand explain various principles and advantages of those embodiments.These and other more detailed and specific features are more fullydisclosed in the following specification, reference being had to theaccompanying drawings, in which:

FIG. 1 illustrates an example of a network that routes packets throughswitches;

FIG. 2A illustrates an example of a packet formatted to route data usingan MPLS label, and FIG. 2B illustrates the MPLS label field of thepacket of FIG. 2A that includes segment IDs for performing segmentrouting in accordance with one embodiment;

FIGS. 3A and 3B illustrate an embodiment of a method for performingsegment routing in a network that uses equipment designed to route datausing multi-protocol label switching (MPLS);

FIG. 4A illustrates a 3-hop example implemented by the method of FIGS.3A and 3B, and FIG. 4B illustrates an embodiment of segment IDs in anMPLS label field for the 3-hop example in accordance with oneembodiment;

FIG. 5 illustrates modifying the MPLS label field in accordance withanother embodiment;

FIG. 6 illustrates modifying the MPLS label field in accordance with yetanother embodiment;

FIG. 7 illustrates modifying the MPLS label field in accordance with oneembodiment;

FIG. 8 illustrates a 6-hop example implemented by the method of FIGS. 3Aand 3B;

FIG. 9 illustrates an example of a packet with multiple MPLS labelfields that includes segment IDs for performing the 6-hop example ofFIG. 8 according to one embodiment; and

FIG. 10 illustrates an embodiment of a source node for generating apacket header in accordance with one or more of the embodimentsdescribed herein.

DETAILED DESCRIPTION

It should be understood that the figures are merely schematic and arenot drawn to scale. It should also be understood that the same referencenumerals are used throughout the figures to indicate the same or similarparts.

The descriptions and drawings illustrate the principles of variousexample embodiments. It will thus be appreciated that those skilled inthe art will be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of theinvention and are included within its scope. Furthermore, all examplesrecited herein are principally intended expressly to be for pedagogicalpurposes to aid the reader in understanding the principles of theinvention and the concepts contributed by the inventor to furthering theart and are to be construed as being without limitation to suchspecifically recited examples and conditions. Additionally, the term,“or,” as used herein, refers to a non-exclusive or (i.e., and/or),unless otherwise indicated (e.g., “or else” or “or in the alternative”).Also, the various embodiments described herein are not necessarilymutually exclusive, as some embodiments can be combined with one or moreother embodiments to form new embodiments. Descriptors such as “first,”“second,” “third,” etc., are not meant to limit the order of elementsdiscussed, are used to distinguish one element from the next, and may beinterchangeable.

Embodiments disclosed herein relate to a system and method forperforming segment routing in a communications network that usesequipment designed to route data using multi-protocol label switching(MPLS). Segment routing is an evolution of MPLS that retains MPLSswitching equipment. In the disclosed embodiments, segment routing maybe performed using MPLS communication equipment by compressing thesegments used to perform segment routing into the header of a datapacket that conforms to the MPLS protocol. Because the segments aresignificantly smaller in size than the fixed-length of an MPLS label(for which a corresponding field of the packet header is designed toaccept), multiple segments may be inserted into one MPLS header field inorder to facilitate a plurality of corresponding hops among nodessituated between source and destination nodes in the network. When thepacket includes multiple MPLS header fields, even more segments may beinserted into the packet to support segment routing using MPLSequipment. As a result, segment routing may be implemented within theframework of an MPLS protocol, thereby increasing the versatility of thenetwork especially in cases where segment routing may be preferable toMPLS routing for certain applications.

FIG. 1 illustrates an example of a network that includes a source node10 and a destination node 20, also labeled Node A and Node Brespectively. In a typical scenario, one or more intervening nodes arearranged between the source and destination nodes. In this example,three intervening switches 30, 40, and 50 are depicted, which may alsobe referred to as switches SW1, SW2, and SW3. A different number ofintervening switches may be included in another embodiment. Operation ofthe network switches and nodes for purposes of routing packets may becontrolled, at least in part, by a software-defined network (SDN)controller 80. The SDN controller may generate and manage lookup tablesthat are to be sent to and used by the nodes in performing routingoperations based on the routing information in each packet header.Connections between the SDN controller 80 and the nodes are illustratedby corresponding signal lines 70 ₁ to 70 ₅ in this example. (In oneembodiment, the intervening switches may be nodes).

The source node 10 includes a processor for generating segmentidentifications (IDs) that specify the intervening nodes 30, 40, and 50and the destination node 20. In one embodiment, the segment IDs identifythe routing addresses of corresponding ones of the intervening anddesignation nodes. As will become apparent below, each segment ID may becompressed into a fixed number of bits (e.g., 6 bits) that issubstantially smaller than the fixed bit-length (e.g., 20 bits) of anMPLS label, in order to allow multiple segment IDs for performingsegment routing to be inserted into the header field of a packetformatted for holding an MPLS label.

FIG. 2A illustrates an example of a packet formatted to route data usingan MPLS label. Referring to FIG. 2A, the packet includes a header 210and a payload 220. The header 210 includes a number of fields includingan MPLS label field 230 and two additional fields F1 and F2 that maystore, for example, various flags and/or other information. In oneembodiment, the flag may store one or more bits indicating whether thepacket is to be routed based on an MPLS technique or whether the packetis to be routed using a segment routing technique. The MPLS label fieldstores a 20-bit label which conforms to the MPLS protocol. The 20-bitlabel is a global label which indicates the information that is to beused to route the packet between the source node 10 and the destinationnode 20. In this example, the packet header only includes one MPLSlabel. In other cases, the packet header may include a plurality of MPLSheaders when, for example, additional routing information is to be usedin routing the packet. The payload 220 stores the data for the packet.

FIG. 2B illustrates an example of how the MPLS label field of the packetheader of FIG. 2A may be modified to include segments for performingsegment routing in accordance with one or more embodiments. In thisexample, the source node 10 has generated the packet to include threesegments (for performing segment routing) in the MPLS label field 230.The three segments may be identified, for example, based on routingtable information (e.g., obtained from the SDN controller 80) thatstores segment IDs for the segments (or hops) between the source anddestination nodes.

Initially, the source node 10 determines routing information for (e.g.,output port number leading to) the first intervening node (first switch)30, for example, based on knowledge of the destination node. Thisrouting information may be determined, for example, by informationstored in a routing table of source node 10.

In the MPLS label field 230, the first segment ID 231 identifies routinginformation to be used in transmitting the packet along a path leadingto the second intervening node (or switch) 40. The second segment ID 232identifies routing information to be used in transmitting the packetfrom the second intervening node 40 along a path leading to the thirdintervening node (or switch) 50. The third segment ID 233 identifiesrouting information to be used in transmitting the packet from the thirdintervening node (or switch) 50 along a path leading to the destinationnode 20 (or when the packet includes multiple MPLS label fields to thenext intervening node (or switch). An example of this latter case willbe discussed in greater detail below). Collectively, when arranged inthe MPLS label field(s), the segment IDs may be considered to beconfigured in a stack. In one embodiment, the routing informationindicated by the segment IDs in the MPLS label field may indicate outputports of corresponding ones of the applicable nodes or switches.

In this embodiment, each of the segment IDs may be compressed toinformation that is 6 bits in length. This bit length may be fixed foreach segment ID, but a different bit length may be used in anotherembodiment. Because each of the three compressed segment IDs in the MPLSlabel field is 6 bits in length, inserting the three compressed segmentIDs into the MPLS label field will not occupy all of the fixed 20-bitlength of this field. Therefore, in accordance with one or moreembodiments, the remaining two bits (e.g., at bit positions 1 and 2) maybe padded zeros or some other null value. Each of the nodes in thenetwork may be programmed or otherwise configured to interpret the lasttwo bits as padded bits when used to perform segment routing.

FIGS. 3A and 3B illustrate an embodiment of a method for performingsegment routing in a communications network that uses equipment designedto route data using multi-protocol label switching (MPLS). The methodmay be explained, for example, with reference to the network of FIG. 1,which has been modified to include compressed segment IDs for 3-hops asset forth in FIG. 4A.

Referring to FIGS. 3A, 3B, and 4A, the method includes, at 310,receiving a request to transmit a packet from the source node 10 to thedestination node 20 through a network that includes MPLS routingequipment. The request may include information indicating whethertransmission of the packet through the network is to be performed usingMPLS routing or segment routing. The network may be, for example, theinternet, a virtual private network, or another type of network thatsupports multiple routing and communication protocols. The request maybe received from a processor of the source node, for example, from ahost system, which, for example, may be a computer, smart phone, server,or another device. The destination node may be coupled, for example, toa similar device for viewing or using the packet data.

At 320, the processor of the source node may determine the identity ofthe destination node based on information in the request. In oneimplementation, the processor of the source node may receive aninstruction or may be programmed with control software to transmit thepacket through the network using segment routing. In this case, theprocessor may identify segment IDs that correspond to switches betweenthe source and destination nodes that are to be used to route the packetthrough the network. The segment IDs may be determined, for example, byreferencing a routing table stored at the source node or otherwiseaccessed from the SDN controller.

As illustrated in FIG. 4A, in this example three segment IDs for therespective switches 30, 40, and 50 have been identified identifying thenext hops for transmitting the packet. Each of the switches may havemultiple input and output ports. In one embodiment, the segment IDs mayindicate the number of the output port of respective ones of theswitches. The output port number of each port indicates to which switchthe packet is to be transmitted. Thus, for example, the routing tablemay indicate that switch (SW) 30 is to transmit the packet through itsoutput port numbered 23, switch (SW2) 40 is to transmit the packetthrough its output port numbered 53, and switch (SW3) 50 is to transmitthe packet through its output port numbered 13, which leads to thedestination node (Node B) 20. The identity of the switches and thecorresponding output port numbers may be determined by the processor ofthe source node with reference to the lookup table received from the SDNcontroller.

At 330, once the segment IDs have been identified, the segment IDs maybe compressed into an N-bit format. In one embodiment, the value of Nmay be 6 but may be a different number in another embodiment. In oneembodiment, operation 330 may be considered to be an optional featurewhen, for example, the routing table already stores the segment IDs inan N-bit compressed format. In one example, compressing the segment IDsmay involve identifying or mapping the output port of the nodes orswitches in an N bit format.

At 340, the processor of the source node 10 inserts the compressedsegment IDs into an M-bit MPLS label field 230 in the header of thepacket to be transmitted to an intermediate node. In this example, thevalue of M is 20 and the compressed segment ID for switch (SW1) 30 is010111, which is the binary value of the output port number 23 that isto be used to transmit the packet to switch (SW2) 40. The compressedsegment ID for switch (SW2) 40 is 110101, which is the binary value ofthe output port number 53 that is to be used to transmit the packet toswitch (SW3) 50. The compressed segment ID for switch (SW3) 50 is001101, which is the binary value of the output port number 13 that isto be used to transmit the packet to the destination node (Node B) 20.The compressed segment IDs are shown in sequence 405 in FIG. 4B.

The segment IDs may be inserted into the MPLS label field 230 in apredetermined order. For example, the segment IDs for the switches maybe stacked into the MPLS label field in sequential order, starting fromthe switch (SW) 30 closest to the source node 10. Thus, as illustratedin FIG. 4B, the segment ID (010111) for switch (SW1) 30 is inserted intobit positions 15 to 20 of a first sub-field 410 of the MPLS label fieldof the packet header, the segment ID (110101) for switch (SW2) 40 isinserted into bit positions 9 to 15 of a second sub-field 420 of theMPLS label field of the packet header, and the segment ID (001101) forswitch (SW3) 50 is inserted into bit positions 3 to 8 of a thirdsub-field 430 of the MPLS label field of the packet header. The finaltwo bits (at positions 1 and 2) of the MPLS label field are padded withzeros. In addition to these features, the processor of the source nodemay insert one or more flag bits indicating that the packet is subjectto segment routing, as opposed to MPLS routing. The one or more flagbits may be stored, for example, in one of the F1 or F2 header fieldsillustrated in FIG. 2B. Additionally, the processor of the source nodemay load the data to be transmitted into the payload portion of thepacket, along with any other control or other packet information to beincluded.

At 350, once the packet has been prepared, the source node 10 transmitsthe packet to the first switch (SW1) 30 through an output portdesignated by the processor. The first switch (SW) 30 may be consideredto be an intermediate node, as well as switches 40 and 50 discussedbelow. As in other cases, the output port used to transmit the packetmay be determined, for example, based on information in a routing tablestored locally at the source node, which information is set by thenetwork SDN controller 80.

At 360, a processor in the first switch (SW1) 30 retrieves the bitvalues corresponding to the compressed segment ID in the first sub-fieldof the MPLS label field. In this case, the compressed segment ID in thefirst sub-field is 010111. Once retrieved, at 361, the processor of thefirst switch 30 may decompress and decode the compressed segment ID(010111) to determine the port number (23) of the first switch throughwhich the packet is to be transmitted to next switch 40. This operationmay be performed by looking up the decompressed and decoded segment IDin a lookup table 510 stored at the first switch. This lookup function,first, confirms that the segment ID is a valid segment ID and, second,identifies port 23 as the proper output port for the first switch 30.The processor of switch 30 may be informed that the information in theMPLS label field contains segment IDs (as opposed to an MPLS label), forexample, based on a predetermined value set in the packet header.

At 362, the processor of switch 30 may retrieve all the bits in the MPLSlabel field in order to determine the output port number (010111) 505.These bits correspond to the incoming MPLS label 520 of FIG. 5. Thecompressed segment IDs in the other two sub-fields of the MPLS labelfield may also be checked to determine whether they are all the samevalues, e.g., whether they are all zeros. If all zeros, the processor ofswitch 30 determines that switch 30 is the last hop and thattransmission of the packet through its output node will flow to thedestination node. In this example, the compressed segment IDs in theincoming MPLS label are not all zeros, so the processor of switch 30proceeds to the next operation.

At 363, the processor of switch 30 pops (e.g., removes from the stack inthe MPLS label field) the compressed segment ID corresponding to itsoutput port. In the example of FIG. 5, this involves removing 010111from the first sub-field of the MPLS label field.

At 364, the compressed segment IDs in the second and third sub-fields ofthe MPLS label field are then shifted to the left, so that thecompressed segment ID that was in the second sub-field is now in thefirst sub-field and the compressed segment ID that was in the thirdsub-field is now in the second sub-field. The third sub-field is thenfilled with all zeros. The result is shown as the outgoing MPLS label at550: 11010100110100000000. In one embodiment, the shifting operation maybe implicitly included in popping operation 363, e.g., the poppingoperation may effectively perform level shifting. In this case,operation 364 would be therefore automatically performed in operation363, and thus process flow may pass from operation 363 to operation 365without operation 364 being separately performed.

At 365 the processor of switch (SW1) 30 pushes the newly createdoutgoing MPLS label into the MPLS label field of the packet andtransmits the packet to the second switch (SW2) 40 through thedesignated output port (port number 23) of the first switch. These popand push operations effectively result in replacing the compressedsegment IDs in the received packet header with a modified shiftedversion that has one of the compressed segment IDs stripped off andsubstituted with a corresponding number of additional padded zeros. Theprocess of FIG. 3B is then repeated at the next node along the path thatreceives the packet.

For example, as illustrated in FIG. 6, a processor of switch 40 receivesthe following incoming label 620 in the MPLS label field of the packetreceived from the first switch 30: 11010100110100000000. The processorretrieves the compressed segment ID (110101) from the first sub-field ofthe MPLS label field, decompresses and decodes this segment ID, and thenlooks up the segment ID in its lookup table 610 (derived from the SDNcontroller) for validation and confirmation. In this case, the processorof the second switch 40 determines that it should transmit the packetthrough its output port number 53, which is the binary value of 110101indicated at 630.

At this point, the processor of the second switch may retrieve the bitvalues in the remaining portions of the MPLS label field and determineif those bit values are all zero. If all zeros, the processor of thesecond switch determines that there are no more hops. In this case, thebit values in the remaining portions of the MPLS label field are not allzeros. Therefore, the processor pops the compressed segment ID (110101)in the first sub-field of the MPLS label, shifts the compressed segmentID in the second sub-field into the first sub-field, and fills thesecond sub-field with all zeros. The result is shown as the outgoingMPLS label at 640: 00110100000000000000. The outgoing MPLS label is thenpushed into the MPLS label field of the packet and the packet istransmitted through output port number 53.

Operations performed as previously described are now performed at switch50. As illustrated in FIG. 7, a processor of switch 50 receives thefollowing incoming label 720 in the MPLS label field of the packetreceived from the first switch 30: 00110100000000000000. The processorretrieves the compressed segment ID (001101) from the first sub-field ofthe MPLS label field, decompresses and decodes this segment ID, and thenlooks up the segment ID in its lookup table 710 (derived from the SDNcontroller) for validation and confirmation. In this case, the processorof the second switch 50 determines that it should transmit the packetthrough its output port number 13, which is the binary value of 001101indicated at 730.

At this point, the processor of the third switch 50 may retrieve the bitvalues in the remaining portions of the MPLS label field and determineif those bit values are all zero. In this case, the check performed inoperation 362 indicates that the bit values are all zeros. As a result,the processor of the third switch determines that there are no more hopsand that transmission of the packet through port 13 will lead to thedestination node (Node B) 20 (or the next node or switch in the casewhere there are multiple MPLS label fields in the packet header). Inthis case, the processor may pop the incoming MPLS label field. At 370,when the packet is transmitted through output port number 13 of thethird switch, the segment routing is complete for that MPLS label. Ifthere are no more MPLS labels in the packet, then segment routing iscomplete for the entire packet.

FIG. 8 illustrates a six-hop example of the method for performingsegment routing in a communications network that uses equipment designedto route data using multi-protocol label switching (MPLS). In thisexample, the first three hops correspond to the same switches in theexample of FIG. 4A. The last three hops correspond to output portnumbers 110011 (51), 111011 (59), and 101010 (21), respectively. Theswitches 840 to 890 corresponding to the six hops are arranged between asource node 810 and a destination node 820. An SDN controller 830 isused to maintain and download the lookup tables to the nodes andswitches to supply the routing information need to transmit packets atrespective points along the network path.

FIG. 9 illustrates an example of the format of a packet routed accordingto the method of FIG. 8. In order to perform segment routing for sixhops (or equivalently, through six switches SW1 to SW6), the packetformat includes multiple MPLS label fields in the header 910. Data forthe packet is included in the payload portion 920.

In the example of FIG. 9, header 911 includes a first MPLS label field911 and a second MPLS label field 912 which may have the same format.For example, each of the MPLS label fields may include three sub-fieldsSF1 to SF3 and a trailing sub-field with padded zeros (marked by the Xregion). The sub-fields in the first MPLS label field 911 storecompressed segment IDs in sequential order for the first three hopscorresponding to switches SW1 to SW3 in FIG. 8. The sub-fields in thelast MPLS label field 912 store compressed segment IDs in sequentialorder for the last three hops corresponding to switches SW4 to SW6 inFIG. 8. Referring again to FIG. 8, section 825 shows the bits values forthe compressed segment IDs in the MPLS label fields 911 and 912 andsection 835 shows these bit values in tandem, with padded zeros, for theMPLS label fields.

In operation, each switch SW1 to SW6 performs operations analogous tothose performed by the method of the 3 hop embodiments. For example, theprocessor of each switch retrieves the compressed segment ID from thefirst sub-field of the first MPLS label field, decompresses and decodesthis segment ID to determine the output port number of that switch, andthen looks up the segment ID in its lookup table (derived from the SDNcontroller) for validation and confirmation.

At this point, the switch processor may retrieve the bit values in theremaining portions of the first MPLS label field and determine if thosebit values are all zeros. If the bit values are not all zeros, theswitch processor may pop the compressed segment ID in the firstsub-field of the first MPLS label field, shift the bits of the remainingcompressed segment ID(s), and the replace the popped segment ID with allzeros. This process continues at each switch until all of the compressedsegment IDs in the first MPLS label field have been used (e.g., are allzeros), at which time the first MPLS label is popped and an analogousset of operations is performed for the second MPLS label field, untilthe packet reaches the destination node.

FIG. 10 illustrates an embodiment of a source node for generating apacket header in accordance with one or more of the embodimentsdescribed herein. The source node may include a processor 1010, a memory1020, and a database 1030. The processor 1010 manages the operations ofthe source node based on algorithms stored in the memory 1020. At leasta portion of these algorithms are executed by the processor 1010 tocontrol the performance of segment routing in accordance with the methodembodiments described herein.

For example, the processor 1010 may execute these algorithms to insertcompressed segment IDs into one or more MPLS label fields in the headerof a packet. The segment IDs may be derived from a lookup table and/orother information obtained, for example, from an SDN controller aspreviously described. Information corresponding to the segment IDs maybe stored in the database 1030 in already compressed or uncompressedform. In this latter case, the processor 1010 may compress the segmentIDs received from the database, for purposes of inserting them intorespective sub-fields in the MPLS label field(s) of a packet header. Thenumber of MPLS label fields in any given packet header may depend, forexample, on the number of hops (or intervening switches) that arebetween the source and destination nodes. Previously, a 3-hop examplerequiring one 20-bit MPLS label field per packet header and a 6-hopexample requiring two 20-bit MPLS label fields per packet header werediscussed. In other embodiments, more than two MPLS label fields may beincluded in a packet header when the number of hops exceeds six. Also, a2-hop case may be executed where the third sub-field in the MPLS labelheader is filled with zeros or some other null value.

In addition to these features, the source node may include an inputinterface 40 and an output interface 50. The input interface 40 mayreceive signals and other information from an SDN controller andincoming packets from other nodes or switches of a network 1080. Theoutput interface 50 may pass outgoing packets prepared by the processor1010 to other nodes and switches in a network 1090, which may be thesame as or different from network 1080. In one embodiment, the switchesbetween the source and destination nodes may themselves be considered tobe nodes. In this case, the switches (and the destination node, for thatmatter) may have the same structure as the source node of FIG. 10,except that additional algorithms are included in memory to control theprocessor to perform pop, shift, replacement, push, and other operationsas described herein.

In accordance with another embodiment, a non-transitorycomputer-readable storage medium stores instructions for controlling aprocessor to perform the operations of the embodiments described herein.At least some of the instructions correspond to the algorithms stored inmemory 1020 of the source node. These and/or other instructions may beimplemented by the SDN controller, processors of the switches, nodecontrollers, and/or other processing devices arranged along the networkpath carrying packets configured as described herein. Thecomputer-readable medium may be, for example, a read-only memory, arandom-access memory, a flash memory, network-attached storage, storagearea network, or another type of storage device capable of storingsoftware, firmware, and/or other instructions for implementing theembodiments described herein.

The processors, controllers, switches, routers, lookup tables, and othersignal-generating and signal-processing features of the embodimentsdisclosed herein may be implemented in logic. When implemented at leastpartially in hardware, the processors, controllers, switches, routers,lookup tables, and other signal-generating and signal-processingfeatures may be, for example, any one of a variety of integratedcircuits including but not limited to an application-specific integratedcircuit, a field-programmable gate array, a combination of logic gates,a system-on-chip, a microprocessor, or another type of processing orcontrol circuit.

When implemented in at least partially in software, the processors,controllers, switches, routers, lookup tables, and othersignal-generating and signal-processing features may include, forexample, a memory or other storage device for storing code orinstructions to be executed, for example, by a computer, processor,microprocessor, controller, or other signal processing device. Thecomputer, processor, microprocessor, controller, or other signalprocessing device may be those described herein or one in addition tothe elements described herein. Because the algorithms that form thebasis of the methods (or operations of the computer, processor,microprocessor, controller, or other signal processing device) aredescribed in detail, the code or instructions for implementing theoperations of the method embodiments may transform the computer,processor, controller, or other signal processing device into aspecial-purpose processor for performing the methods herein.

It should be apparent from the foregoing description that variousexemplary embodiments of the invention may be implemented in hardware.Furthermore, various exemplary embodiments may be implemented asinstructions stored on a non-transitory machine-readable storage medium,such as a volatile or non-volatile memory, which may be read andexecuted by at least one processor to perform the operations describedin detail herein. A non-transitory machine-readable storage medium mayinclude any mechanism for storing information in a form readable by amachine, such as a personal or laptop computer, a server, or othercomputing device. Thus, a non-transitory machine-readable storage mediummay include read-only memory (ROM), random-access memory (RAM), magneticdisk storage media, optical storage media, flash-memory devices, andsimilar storage media and excludes transitory signals.

It should be appreciated by those skilled in the art that any blocks andblock diagrams herein represent conceptual views of illustrativecircuitry embodying the principles of the invention. Implementation ofparticular blocks can vary while they can be implemented in the hardwareor software domain without limiting the scope of the invention.Similarly, it will be appreciated that any flow charts, flow diagrams,state transition diagrams, pseudo code, and the like represent variousprocesses which may be substantially represented in machine readablemedia and so executed by a computer or processor, whether or not suchcomputer or processor is explicitly shown.

Accordingly, it is to be understood that the above description isintended to be illustrative and not restrictive. Many embodiments andapplications other than the examples provided would be apparent uponreading the above description. The scope should be determined, not withreference to the above description or Abstract below, but should insteadbe determined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled. It isanticipated and intended that future developments will occur in thetechnologies discussed herein, and that the disclosed systems andmethods will be incorporated into such future embodiments. In sum, itshould be understood that the application is capable of modification andvariation.

The benefits, advantages, solutions to problems, and any element(s) thatmay cause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeatures or elements of any or all the claims. The invention is definedsolely by the appended claims including any amendments made during thependency of this application and all equivalents of those claims asissued.

All terms used in the claims are intended to be given their broadestreasonable constructions and their ordinary meanings as understood bythose knowledgeable in the technologies described herein unless anexplicit indication to the contrary in made herein. In particular, useof the singular articles such as “a,” “the,” “said,” etc. should be readto recite one or more of the indicated elements unless a claim recitesan explicit limitation to the contrary.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various embodiments for the purpose of streamliningthe disclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive subject matter lies in less than allfeatures of a single disclosed embodiment. Thus the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separately claimed subject matter.

What is claimed is:
 1. A method for controlling packet routing in anetwork, comprising: identifying segment identifications (IDs) for anumber of switches; arranging a first number of the segment IDs into afirst field of a packet, wherein the first field is a firstmulti-protocol label switching (MPLS) label field that is M bits inlength, each of the segment IDs being represented by N bits in lengthand identifying an output port of a respective one of the number ofswitches located along a network path between a source node and adestination node, and M is greater than a cumulative sum of respectiveNs for the first quantity of segment IDs; and padding the first MPLSlabel field with one or more predetermined values for bits unoccupied bythe segment IDs.
 2. The method of claim 1, wherein the first number ofsegment IDs are arranged in the first MPLS label field in an ordercorresponding to a sequence of a path of traversed switches on thenetwork path.
 3. The method of claim 1, wherein the one or morepredetermined values are zeros.
 4. The method of claim 1, wherein thefirst number of the segment IDs arranged into the first MPLS label fieldcorresponds to all of the switches on the network path between thesource node and the destination node.
 5. The method of claim 1, whereeach of the N-bit representations are a compressed version of therespective segment IDs.
 6. The method of claim 5, further comprising:arranging a second number of the segment IDs into a second MPLS labelfield.
 7. The method of claim 1, further comprising: identifying thesegment IDs based on information in a routing table.
 8. A method forcontrolling packet routing, comprising: receiving a packet at a switchof a data network; accessing first routing information from the packet;modifying the packet to include second routing information; andtransmitting the packet from the switch based on the first routinginformation, wherein the packet includes a first multi-protocol labelswitching (MPLS) label field from which the first routing information isaccessed, the first routing information including a first segmentidentification (ID) and at least a second segment ID, and whereinmodifying the packet includes replacing the first routing informationwith the second routing information by replacing the first segment IDwith one or more predetermined values in the first MPLS label field, thesecond routing information omitting the first segment ID and includingat least the second segment ID, and the packet transmitted from theswitch is based on the first segment ID.
 9. The method of claim 8,wherein the one or more predetermined values are zeros.
 10. The methodof claim 8, wherein replacing the first routing information with thesecond routing information includes shifting a position of the at leastsecond segment ID in the first MPLS label field.
 11. The method of claim10, wherein the second routing information includes padded zerosincluded with the shift position of the at least second segment ID inthe first MPLS label field.
 12. The method of claim 8, furthercomprising: determining an output port number based on the first segmentID, wherein transmitting the packet based on the first routinginformation includes transmitting the packet through the output portnumber.
 13. A system for controlling packet routing in a network,comprising: a memory configured to store computer instructions; and aprocessor configured to execute the computer instructions to: identifysegment identifications (IDs) for a number of switches, and arrange afirst number of the segment IDs into a first field of a packet, whereinthe first field is a first multi-protocol label switching (MPLS) labelfield that is M bits in length, each of the segment IDs beingrepresented by N bits in length and identifying an output port of arespective one of the number of switches located along a network pathbetween a source node and a destination node, M is greater than acumulative sum of respective Ns for the first quantity of segment IDs,and the processor is configured to pad the first MPLS label field withone or more predetermined values for bits unoccupied by the segment IDs.14. The system of claim 13, wherein the processor is configured toarrange the first quantity of segment IDs in the first MPLS label fieldin an order corresponding to a sequence of a path of traversed switcheson the network path.
 15. The system of claim 13, wherein the firstnumber of the segment IDs arranged into the first MPLS label fieldcorresponds to all of the switches on the network path between thesource node and the destination node.
 16. The system of claim 13,wherein the processor is configured to arrange a second number of thesegment IDs into a second field of the packet when the number ofswitches is greater than three, and wherein the second field of thepacket is a second MPLS label field.
 17. A system for controlling packetrouting in a network, comprising: a memory configured to store computerinstructions; and a processor configured to execute the computerinstructions to: identify segment identifications (IDs) for a number ofswitches, and arrange a first number of the segment IDs into a firstfield of a packet, wherein the first field is a first multi-protocollabel switching (MPLS) label field that is M bits in length, each of thesegment IDs being represented by N bits in length and identifying anoutput port of a respective one of the number of switches located alonga network path between a source node and a destination node, M isgreater than a cumulative sum of respective Ns for the first quantity ofsegment IDs, the first MPLS field has a length of M bits, and each ofthe first number of segment IDs is compressed into N bits, where M≥3·N.